This application claims the benefit of the Korean Application No. 2002-0000276 filed on Jan. 3, 2002, which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates, in general, to a process of forming a micro-pattern of a metal or a metal oxide, and more particularly, to a process of forming a micro-pattern of a metal or a metal oxide, wherein a metal complex is used which exhibits a difference of solubility depending on the degree of exposure to light having a particular wavelength.
2. Description of the Prior Art
As is well known to those skilled in the art, a patterned thin film formed on a substrate using materials having different electrical properties has been applied to various electronic devices. In an electronic device production process, a metal thin film is generally coated on a substrate such as a crystallized silicone wafer and then patterned.
A conventional method of forming a metal pattern comprises the steps of applying an organometallic compound on a surface of a silicone or glass substrate using a chemical vapor deposition process or an atomic layer deposition process to form a thin film on the substrate; coating a photoresist on the resulting organometallic film according to a spin coating process; patterning the resulting photoresist film according to a photolithography process; and etching the patterned photoresist film.
Another conventional method of forming a metal pattern comprises the steps of depositing a metal film on a substrate according to a plasma deposition process, a sputtering process, or an electric plating process; coating a photoresist on the resulting metal film; patterning the photoresist film using light; and etching the patterned photoresist film to reveal a desired metal pattern. Unfortunately, these conventional methods require conditions of high temperature and a vacuum, and essentially involve a patterning step using a photoresist and an etching step for removing the photoresist, thus having the disadvantage of a high production cost due to such a complicated process. Other disadvantages of these conventional methods are that the resolution of the resulting pattern is inevitably reduced because the patterning and etching steps are typically repeated several times, and that the surface of a deposited metal film is not smooth, causing these conventional methods to additionally require a flatting step.
Meanwhile, various methods of forming a metal pattern without using a photoreaction have been suggested. For example, Japanese Patent Publication No. 62-263973 discloses a method of forming a metal pattern, in which an electronic beam is irradiated on a thin film of a metal complex without inducing any photoreaction. In addition, U.S. Pat. No. 5,064,685 discloses a method of forming a metal thin film using a thermal decomposition reaction, comprising the steps of applying a metal complex-containing ink on a substrate; and heating the resulting substrate with the use of a laser beam. According to this patent, the substrate is exposed to a high temperature, and materials other than metals are prevented from being deposited on the substrate.
On the other hand, U.S. Pat. No. 5,534,312 describes that a metal pattern can be made through coating a substrate with a metal complex, prepared by bonding one or more photosensitive organic ligands to one or more metal atoms, and exposing the coated substrate directly to electromagnetic radiation without applying a photosensitive resin on the coating film of the metal complex. The metal complex essentially consists of at least one ligand selected from the group consisting of: acetylacetonates (both substituted and unsubstituted); dialkyldithiocarbamates; carboxylate; pyridines; amines; diamines; arsines; diarsenes; phosphines; diphosphenes; arenes; alkoxy ligands; alkyl ligands; and aryl ligands. Particularly, in the case that the complex comprises more than one ligand, at least one of the ligand is selected from the group consisting of: oxalato; halogens; hydrogen; hydroxy; cyano; carbonyl; nitro; nitrito; nitrate; nitrosyl; ethylenes; acetylenes; thiocyanato; isothyocyanato; aquo; azides; carbonato; amines; and, thiocarbonyl. When exposed to electromagnetic radiation, the metal complex goes through a photochemical reaction resulting in the dissociation of the organic ligands from the central metal atoms, to produce a new metal-containing material adherent to the substrate. However, this patent is disadvantageous in that the rate of such transformation is relatively low, and consequently many hours are required to complete the patterning process. Other disadvantages are that ligand contamination is likely to occur because the separation of the ligands from the metal completely depends on photoreaction, and that, if the final film consists of a metal oxide, the oxide film should be reduced and annealed under a mixed gas of hydrogen with nitrogen at 200° C. or higher for 30 minutes to several hours so as to improve the conductivity of the film. Additionally, the organic ligands constituting the metal complex have so large a steric hindrance, and consequently occupy so large a space as to result in a large percentage of contraction in the thickness of the resulting metal film upon their decomposition by exposure to light.